Add stats output to multiqc

[lpantano]

Add a module for multiqc tool that parses the example stats file so it can be integrated in multiqc report.

Ideally, we need to add first a commented line like this when creating the stats file:

# mirtop stats version X samples: s1, s2 ,s2 ....

This can go here: https://github.com/miRTop/mirtop/blob/dev/mirtop/gff/stats.py#L17

[lpantano]

done by @oneillkza: https://github.com/ewels/MultiQC/issues/788